The safety of passengers in vehicle seats in relation to the possibility of a high-speed catastrophic impact, such as an aircraft crash, has been high on the list of concerns for safety designers for years. Another kind of serious impact event, not widely experienced, but very threatening to military personnel who ride in extremely high-speed sea-going small vessels is a downward thrust into rough water approximating, or in fact replicating, a so-called State-III sea condition. Other kinds of similar events will also come to mind. Frequently, the key cause of death or disabling injury from an event of this nature is axial compression-overload (in excess of about 1500-lbs) to the spine. Many different approaches have been conceived and implemented to deal with events such as those just mentioned, but despite numerous efforts to date, there still occur large numbers of seat/impact, spinal-compression fatalities and serious injuries, solutions to which seem to be intractable in terms of minimization, let alone significantly resolution.
As suggested above, these disabling and fatal spinal injuries to seated vehicle occupants are usually traceable to high-G compression forces that are delivered axially (longitudinally) through the spine as a consequence of a crash, or crash-like, impact. Fundamentally, these forces come about because of the extraordinarily high decelerations which are experienced on account of the “downward” axial speed, and the resulting downward axial deceleration, of the spine beginning at the moment of, and thereafter developing in the few fragments of a second after (for example about 50-ms), initial impact.
The present invention takes square aim at this serious problem, and does so in a manner which may initially strike one as being significantly counter- or non-intuitive, and even incorrect in approach. Very specifically, what is proposed by the present invention is a specialized safety seat structure and methodology which utilize, in combination, an anti-spring-back seat platform, i.e. a very rigid seat platform, which is anchorable to the frame in a vehicle, and a triggerable, explosively reactive, upward acceleration structure which responds tiny fragments of a second (within about 50-ms) after a catastrophic downward impact and deceleration to propel a seat occupant upwardly away from whatever forms the underlying, supporting seat platform in the seat structure. This explosive upward acceleration introduces, importantly, a lower G-value (preferably just under about 15-G) than those forces which would otherwise typically be experienced following initiation of such an impact. The effect of the thus proposed upward acceleration is to diminish the effective downward velocity and the “downward deceleration” of the spine as a full-impact crash, or crash-like, event rapidly unfolds.
Test results of laboratory-sensitized human-form dummies, which have been subjected to this kind of an event repeatedly, have shown that axial compressive forces introduced into the spine during impact, with the present invention in place and operating, are in fact below the limit (about 20-G) which is recognized usually to cause serious spinal injury and/or a fatality as a consequence of such an impact.
As was mentioned above, the preferred form of the invention includes the basic combination just stated—a rigid seat platform, and a triggerable and explosive upward acceleration structure. It may also preferably include, in the interface between (a) whatever specific mechanism is employed to initiate upward acceleration, and (b) a seated occupant, a “sit upon” cushioning structure characterized with a behavior known as acceleration-rate-sensitivity—a characteristic which causes such a material to behave more and more like a solid as accelerative compression forces delivered through it increase in level.
While many different kinds of explosively active and triggerable upward acceleration mechanisms/structures may be employed successfully in the implementation and practice of the invention, the current preferred approach for implementing this invention involves using otherwise relatively conventional, explosively triggerable air-bag technology. The accelerations (not specifically elaborated herein) produced by this technology have been found to work well in the setting of the present invention. Thus, and in accordance with the preferred manner of implementing the invention, an appropriate undeflated air-bag bladder is suitably installed intermediate a rigid seat frame, or seat frame base, and the underside of an acceleration-rate-sensitive cushioning element, or structure, on top of which a seated occupant sits. An appropriate sensor, typically some form of conventional accelerometer, is incorporated, preferably into the seat base or frame, to respond within fragments of a second (within about 50-ms) after the onset of a downward impact, to initiate (trigger) an explosive inflation of the air bag which is appropriately and conventionally supplied with a source of compressed air, or other pressurized gas.
Though a seated occupant will typically be strapped effectively to the seat structure with a seatbelt harness, experience in the mentioned “dummy” tests has shown that there is sufficient “play” present which allows rapid “explosive” upward acceleration of an occupant of up to a distance of perhaps about 1-inch. This “play” provides enough freedom of action of the structure of this invention to achieve the desired reduction in downward impact velocity and deceleration which is responsible for producing dangerous compressive forces in a seated occupant's spine.
These and other features and advantages that are attained and offered by the present invention will become more fully apparent as the detailed description which now follows is read in conjunction with the accompanying drawings.